FIG. 1 is a schematic view of a module of an evacuated tubular solar collector 5. The evacuated tubular solar collector 5 comprises a heat pipe 2, a solar heat absorption plate 3, and a vacuum glass tube 4. The heat pipe 2 is a high efficient electric heat element to transfer heat supplied from the solar heat absorption plate 3 collecting solar heat. The vacuum glass tube 4 includes the solar heat absorption plate 3 and the heat pipe 2 in a vacuum, to minimize a loss of heat.
In use of solar energy which is an unlimited energy source, the high efficiency of a solar collector is most important. The high efficiency of the solar collector is obtained, to some extent, by applying the heat pipe as a high efficient electric heat element and the vacuum technology.
However, when the solar energy is not fully transferred even though it is efficiently collected, a high efficient collector becomes useless. In this regard, the transfer of collected heat energy to a water heater through a heating medium flow conduit, without the loss of heat, is another important variable in determining the overall efficiency of use of the solar energy.
Thus, the optimum design of a heat pipe and a manifold which are a primary gateway to transfer the heat acts as a very important variable.
FIG. 2 is a schematic view of a manifold in a conventional evacuated tubular solar collector 5. In the conventional evacuated tubular solar collector 5, a venting pipe 13 is attached to each manifold 1 where heat exchange is performed between a heat medium and a condenser of a heat pipe 2 which is the electric heat element. In a conventional concentric manifold 1, an air vent 14 by the venting pipe 13 is necessarily needed.
Specifically, in a large evacuated tubular solar system, when a heating medium is supplemented to maintain and manage the solar system, an air needs to be removed from each manifold. This increases a manufacturing cost of a collecting module.
Further, an interior shape is a factor to have a primary effect in raising the efficiency of heat transfer, and the condenser of the heat pipe is fully inserted within the manifold, to indirectly supply a heat source through the heating medium flow conduit. However, since thermal efficiency decreases as the heat transfer resistance increases, an amount of the heat being transferred needs to be maximized, by increasing a contact area between the manifold and the heat pipe. However, in the conventional manifold, since entrance/exit of a fluid which is the heating medium are positioned on the center line in a direction in which the fluid flows, the flowing heating medium does not sufficiently contact with the condenser of the heat pipe. As a result, heat is not uniformly transferred from the condenser of the evacuated tubular solar collector.